The present invention relates to a fuel injection amount control device that is employed in an internal combustion engine with a blow-by gas ventilation system.
As an internal combustion engine of a vehicle, there is known an internal combustion engine with a blow-by gas ventilation system. The blow-by gas ventilation system discharges blow-by gas in the crankcase into intake air and burns it in the combustion chamber. In the blow-by gas ventilation system, when the temperature of the engine oil rises after the startup of the internal combustion engine, fuel mixed with the oil is volatilized so that blow-by gas containing a great amount of fuel is discharged into the intake air. As a result, the air-fuel ratio is disturbed.
In the fuel injection amount control device disclosed in Japanese Laid-Open Patent Publication No. 5-202786, the deviation of the air-fuel ratio until a predetermined time elapses from the startup of the internal combustion engine is learned as a dilution learning value, and the fuel injection amount is corrected by the dilution learning value so that disturbance of the air-fuel ratio due to the volatilization of the fuel in oil is suppressed. In accordance with the operation state of the internal combustion engine, the amount of the blow-by gas discharged into the intake air changes and thus the degree of affecting the air-fuel ratio also changes. Thus, in the fuel injection amount control device of the document described above, the learning of the dilution learning value is individually executed for each of learning areas divided according to the operation condition of the internal combustion engine.
However, in this case, the learning of the dilution learning value needs to be individually executed in each learning area. Thus, there is a case in which the learning of the dilution learning value is not completed even when a long time elapses from the startup of the internal combustion engine in the learning area that is likely to be operated rarely. As a result, a long time may be necessary until the air-fuel ratio is stabilized by the learning of the dilution learning value.